Okay, I see what you're saying. I googled the phrase and here's a good example:
http://books.google.com/books?id=dSYuNXmZjFwC&pg=PA137&lpg=PA137&dq="There is no enemy closer than Corinth."
I don't know the solution to things like that. If history is to be written in narrative form, at some point an author needs to make a decision what's accurate, and then write events as if they happened that way. The problem is that one can never be 100% certain what actually happened, yet when written as narrative, it all will sound as if it's endorsed by the author 100%, even though the author may actually only be somewhere between 50 and 100 percent. For very iffy things, an author may add a disclaimer, but too many disclaimers or discussions of alternatives make the narrative unreadable and turn it into a discussion about competing sources instead.
That's why I tend to avoid secondary sources, because it's a quick and painless way to absorb the general sweep of what happened, but one really needs to trace the data back through the footnotes to get a sense of what data they're based on if one is going to endorse the facts within them oneself.
But in
writing secondary sources, how does one avoid the problem? Ideally, everyone would do all the research themselves on anything they were interested in and come up with their own conclusions based on the raw data available, without any intermediary interpretation, but in real life, that's not how people like to consume history.